This invention relates generally to gasification systems, and more specifically, to a solids supply system having a pressure control system, the solids supply system for supplying solid fuel in a gasification system.
At least one known gasification system, such as an integrated gasification combined-cycle (IGCC) plant, includes a fuel supply system that is coupled upstream of a gasifier and that is configured to channel fuel to the gasifier. At least one known fuel is a slurry of powder coal and water. In such a system, the slurry is a viscous liquid that is metered within the fuel supply system and that is delivered at a predetermined pressure to the gasifier. Water is used to facilitate transport of the slurry through the fuel supply system. Accordingly, in such systems, the significant amounts of water used to transport the viscous liquid may impose a thermodynamic penalty on the fuel supply system, the gasifier, or other systems within the IGCC plant. Depending on the system, the penalty imposed may adversely affect the efficiency and capital cost of the IGCC plant.
At least one other known fuel supply system channels a dry fuel, such as coal, to the gasifier. The dry fuel is channeled through a lockhopper that pressurizes the dry coal. Once the lockhopper has pressurized the coal, the coal is then transported through the fuel supply system to the gasifier wherein the fuel is injected into the gasifier. However, instabilities in the control of the flow and pressure of the fuel feed may make it difficult to supply the fuel in a consistent manner. This may result in higher operating and capital costs due to a negative effect on efficiency, increased down time, and the need to use more expensive components.
At least one known feed hopper controls differential pressure between a feed vessel and a reactor using a controller. However, such a control addresses system pressure drop without controlling pressure drops across components of the system. Another known pressure control system controls a feed rate of solids and addresses the system pressure drop without controlling pressure drops across components of the system. Further, the pressure control system requires that a vent line and pressurizing lines be connected to the same header.